The Very Best are on my list of acts to see. I wasn't aware of their existence before they were announced for Fuji, but I checked them out on YouTube after the announcement and liked what I heard.
The tough clashes for me are Yosui Inoue/Yael Naim and Elvis Costello/New Cool Collective. I'm really hoping that Yael Naim and NCC will do another set at a smaller stage (perhaps Yael Naim at Gypsy Avalon, and NCC at Crystal Palace) so that I'll have a chance to see them.
oh.kamikaze - I don't think there are any rules against bringing alcohol into the campsite. No bag searches at the entrance, as far as I can recall. They do search your bag when you enter the festival venue, but I'm not even sure if they're searching for alcohol or just glass bottles (which are definitely banned). As for pot, I've never sought it out so I can't help you there, but I've seen (or rather, smelled) people smoking it plenty of times so I don't imagine it's too difficult. I don't know whether they procure them at the festival or get them elsewhere and smuggle them in. Try to be a little discreet though - Japan isn't very lenient when it comes to pot!
Edit: Or, what spu001 just said...